+29.+ I took a glass retort which was capable of holding 8 ounces of water, and distilled fuming acid of nitre according to the usual method. In the beginning the acid went over red, then it became colourless, and finally all became red again; as soon as I perceived the latter, I took away the receiver and tied on a bladder, emptied of air, into which I poured some thick milk of lime (§ 22) in order to prevent the corrosion of the bladder. I then proceeded with the distillation. The bladder began to expand gradually. After this I permitted everything to cool, and tied up the bladder. Lastly I removed it from the neck of the retort. I filled a bottle, which contained 10 ounces of water, with this gas (§ 30, _e._), I then placed a small lighted candle in it; scarcely had this been done when the candle began to burn with a large flame, whereby it gave out such a bright light that it was sufficient to dazzle the eyes. I mixed one part of this air with three parts of that kind of air in which fire would not burn; I had here an air which was like the ordinary air in every respect. Since this air is necessarily required for the origination of fire, and makes up about the third part of our common air, I shall call it after this, for the sake of shortness, Fire-air; but the other air which is not in the least serviceable for the fiery phenomenon, and makes up about two-thirds of our air, I shall designate after this with the name already known, of Vitiated Air. +30.+ Anyone might ask me in what way I bring air from one vessel into another. I find it necessary therefore to describe this in the first place. My arrangements and vessels are the very simplest that one can possibly have: flasks, retorts, bottles, glasses, and ox bladders are the things which I employ. The bladders, while they are still fresh, are rubbed, and blown up very fully, then tightly tied and hung up to dry. When I wish to use such a bladder and find it blown up just as fully as at first, I am thereby assured that it is tight.